Wear of ultrahigh-molecular-weight polyethylene against titanium-nitride-coated counterfaces

Simple configuration pin-on-plate tests were conducted in order to compare the wear of ultrahigh-molecular-weight polyethylene (UHMWPE) when sliding against titanium-nitride (TiN)-coated wrought cobalt-chromium (Co-Cr) plates obtained by arc evaporative physical vapour deposition (AEPVD) with that which occurs when sliding against uncoated wrought and cast Co-Cr plates. UHMWPE wear was determined for plates in their undamaged form and following simulated third-body damage to produce scratches similar to those observed on retrieved implants. In their undamaged form, the coatings produced a similar wear rate of UHMWPE to that with the uncoated Co-Cr plates. However, in their damaged form, TiN-coated plates showed significantly lower polyethylene wear than uncoated wrought Co-Cr plates (analysis of variance; alpha = 0.05). The TiN-coated plates prevented the generation of high scratch lips due to their higher hardness, producing much smaller R-P values (0.19 mu m) than the scratched uncoated Co-Cr plates (0.92-1.15 mu m). This is a probable explanation for the lower wear rate on the scratched TiN-coated plates than on the scratched uncoated wrought plates. The results of this study have illustrated the possibility of using AEPVD TiN coatings in total knee joint replacements in order to reduce polyethylene wear.